Question: Which means{streak color} at the color {gray} ?
SPARQL (Wikidata): select distinct ?answer where { ?answer wdt:P534 wd:Q42519}
Answer: allanite series, gahnite, argentopyrite, bismutite, enstatite, thortveitite, kamacite, xilingolite, mohite, godlevskite, icosahedrite, clino-ferro-ferri-holmquistite, dorrite, ferri-winchite, milotaite, potassic-ferro-ferri-sadanagaite, fluoro-pargasite, potassic-fluoro-pargasite, ferro-ferri-obertiite, lucchesiite